The present invention relates to a security lock control method for remote control system.
There has been known to the art a security system having a plurality of security devices interconnected via, for example, a communication control wire (bus) complying with a standard such as RS-485 (EIA-485 Standards). Examples of the security device include a surveillance camera, VTR for recording images picked up by the surveillance camera, frame switcher and the like. Each of the security devices is assigned a specific address for discrimination from the other security devices on the bus. The address setting is done, for example, by means of a DIP switch assembly provided at each security device.
The bus with the security devices connected thereto is connected to a controller for remote control of the security devices or for centralized management of conditions of the security devices. For instance, a remote control of a VTR having address xe2x80x9c1xe2x80x9d is done by transmitting a command containing the address xe2x80x9c1xe2x80x9d of the VTR and a control content such as xe2x80x9cPLAYxe2x80x9d or xe2x80x9cEJECTxe2x80x9d.
The controller is also adapted to transmit a control command to all the security devices on the bus at a time. Such a transmission method is known as broadcast transmission. Such a control through broadcast transmission is performed for setting the respective clocks of all the security devices on the bus to the same time of day, for example.
The security system must ensure the prevention of any unauthorized attempt to deactivate any of the security devices performing operations for security purposes. In this connection, some security systems support a controller setting such that the controller can disable the remote control of all the security devices on the bus which are performing the operations for security purposes (activate security lock).
Some security systems are configured to permit connection of plural controllers for remote control from different rooms. The security system configured to permit the connection of plural controllers involves fear that even though a main controller activates the security lock, the security lock may be deactivated by another controller.
To prevent the security lock from being released by another controller, it may be contemplated to set the bus in Busy state by means of the main controller thereby disabling the bus line itself. However, this also disables the controller to obtain useful information from the security devices on the bus.
The useful information includes, for example, alarm information supplied to the controller from the respective devices. Some of the security devices has a function to detect a possibility of occurrence of significant event in terms of security. Upon detection of a possible occurrence of the significant event in terms of security, such a security device transmits alarm information to the controller via a communications control line. Receiving the alarm information from the security device, the controller stores the alarm information in a non-volatile memory such as EEPROM.
It is therefore, an object of the invention to provide a security lock control method for remote control system arranged such that when the main controller is set in remote-control disable mode, communications over the bus are permitted but the electronic devices on the bus are prevented from being remotely controlled through manipulation of a subcontroller.
It is another object of the invention to provide a security lock control method for remote control system arranged such that when a higher priority controller is set in the remote-control disable mode, the communications over the bus are permitted but the electronic devices on the bus are prevented from being remotely controlled through manipulation of a lower priority controller.
According to a first aspect of the invention, a security lock control method for remote control system including electronic devices, one main controller connected to the electronic devices via a bus for remotely controlling the electronic devices, and one or more subcontrollers connected to the electronic devices via the bus for remotely controlling the electronic devices is characterized in that operation modes of each controller include a remote-control enable mode to enable the remote control of all the electronic devices connected to the bus, and a remote-control disable mode to disable the remote control of all the electronic devices connected to the bus; that when an operation is performed to set the main controller in the remote-control disable mode, the main controller sets itself in the remote-control disable mode while informing the subcontrollers that the operation mode of the main controller is transferred to the remote-control disable mode, thereby causing the subcontrollers to set themselves in the remote-control disable mode; that when an operation is performed to set the main controller in the remote-control enable mode, the main controller sets itself in the remote-control enable mode while informing the subcontrollers that the operation mode of the main controller is transferred to the remote-control enable mode, thereby causing the subcontrollers to set themselves in the remote-control enable mode; that when an operation is performed to set any one of the subcontrollers in the remote-control disable mode, the subctontroller sets itself in the remote-control disable mode; and that when an operation is performed to set any one of the subcontrollers in the remote-control enable mode, the subcontroller checks the operation mode of the main controller, then setting itself in the remote-control enable mode if the main controller is in the remote-control enable mode or maintaining itself in the remote-control disable mode if the main controller is in the remote-control disable mode.
It is preferred that when energized, the main controller informs the subcontrollers of its operation mode thereby establishing coincidence in the operation mode of the subcontrollers and the main controller, and that when energized, any one of the subcontrollers checks the operation mode of the main controller for establishing coincidence in the operation mode of the subcontroller and the main controller.
According to a second aspect of the invention, a security lock control method for remote control system including electronic devices and a plurality of controllers connected to the electronic devices via a bus for remotely controlling the electronic devices is characterized in that each of the controllers is previously assigned a priority and has operation modes including a remote-control enable mode to enable remote control of all the electronic devices connected to the bus and a remote-control disable mode to disable the remote control of all the electronic devices connected to the bus; that when an operation is performed to set any one of the controllers in the remote-control disable mode, the controller sets itself in the remote-control disable mode while transmitting to the other controllers a first control command containing a priority thereof; that a controller receiving the first control command sets itself in the remote-control disable mode if the priority contained in the first control command is higher than a priority thereof; that when an operation is performed to set a top priority controller in the remote-control enable mode, the top priority controller sets itself in the remote-control enable mode while transmitting to the other controllers a second control command containing the priority thereof; that when an operation is performed to set any one of the controllers other than the top priority controller in the remote-control enable mode, the controller in question checks the operation mode of any controller higher in priority than itself, then setting itself in the remote-control enable mode and transmitting to the other controllers a second control command containing the priority thereof if the higher priority controller is in the remote-control enable model or maintaining itself in the remote-control disable mode if the higher priority controller is in the remote-control disable mode; and that a controller, receiving the second control command, sets itself in the remote-control enable mode if the priority contained in the second control command is higher than a priority thereof.
It is preferred that if the top priority controller, when energized, is in the remote-control disable mode, the top priority controller transmits to the other controllers the first control command containing the priority thereof; that if the top priority controller is in the remote-control enable mode, the top priority controller transmits to the other controllers the second control command containing the priority thereof; and that when energized, any one of the controllers other than the top priority controller determines whether any of controllers higher in priority than itself operates in the remote-control disable mode or not, then setting itself in the remote-control disable mode if any of the controllers higher in priority than itself is in the remote-control disable mode, or setting itself in the remote-control enable mode if none of the controllers higher in priority than itself is in the remote-control disable mode.